Pump



Oct. 7, 1952 E. L. MIDGETTE 2,612,337

PUMP

Filed May 21, 1946 6 fSheets-Sheej; 1

Fly 7 F138 5 iNVENTOR.

v Ernst LMd'gette 4 BY I Attorney Oct. 7, 1952 WDGETTE 2,612,837

PUMP

Filed May 21, 1946 6 Sheets-Sheet 3 INVENTQR. Ernst L. Midge.

AttOTWqy E. L. MIDG ETTE Oct. 7, 1952 I INVENTOH.

Ernst L. Mx'dgette E. L. MlDG ETTE Oct. 7, 1952 PUMP Filed May 21, 1946 6 Sheets-Sheet 5 INVENTOR. ErnstLMidgefle Attorney Patented Oct. 7, 1952 UNITED STATES PATENT OFFICE PUMP Ernst L. Midgette, Philadelphia, Pa., assignor to American Engineering Company, Philadelphia, 2a., a corporation of Pennsylvania Application May 21, 1946, Serial No. 671,308

.5 C aims- This invention relates to pumps and more particularly to pumps of the radial pistontype.

One object of the present-invention is to provide pumps of a simplified and generally improved construction.

Another object is to provide pumpsof the radial piston type, having rotary cam means ior operating the pistons thereof.

A further object is to provide pump Of the radial piston type, having rotarycammeans for operating the pistons thereof and means-roiadjusting the strokes of said pistons.

A still further object is to provide pumns ef the multi-row radial piston type, having rotary cam means for operating the pistons thereof.

A more specific object is to provide a pump comprising a series of pistons arrangedfor successive operation by cam. means whereby .a con.- tinuous flow of fluid is assured.

A still further object is to providepumps oi the stated character, having improved features of construction which producehighest: operating efiiciencies. I

Other and further objects. will become apparent as the descrip-tionof the inventionprogresses.

Of the drawings:

Fig. 1 is a sectional view construction taken substantially. along line of Fig. 2.

Fig. 2 is an end View, partly in section, thesectional portion being taken substantially along line 2-2 of Fig. 1.

Fig. '3 is a side view, partly in section, of the cam shaft for actuating the-pistons of the pump.

Fig. 4 is an end view of the shaft. showrrin Fig. 3.

Fig. 5 is a sectional view of one of thepistons taken substantially alon line 5-5 .of Fig.6.

Fig. 6 is a sectional view of one of thetpistons taken substantially along line 66 of Fig. 5.

Fig. 7 is a plan view of one of the slippers. associated with the pump.

Fig. 8 is an endview of "the slipper shown. in Fig. 7.

Fig. 9 is a sectional view of a pump ofian' alternative construction taken substantially along line 9-9 of Fig. 10.

, Fig. 10 is a sectional. view takensubstantially along line iii-4 U of Fig-49.

Fig. 11 is a side view, partly insection of a pump of a furthermodified construction.

Fig. 12 is a sectional miewtaken substantially along line l2-l2 of Fig. 11.

of apumpof preferred 1 l Fig. 13 is a sectional aview taken substantially along line l:3-'l 3 of Fig-l1.

Fig. 14 is a sectional view takensubstantially along line i ll4 of Fig. 111.

Fig. 15 is a sectional view takenisubstantially,

along line I 5-1 ioiFigil l.

Fig. 16 is a side elevational view of the cam shaft for the pump shown in Figs. 11 to- 15; and

Fig. 17 is an end view, partly in section, taken elene ine of F 16 Referring to the drawings, the numeral designates a pump, which consists generally of a n 2 herns as r s of adia l iseased c lrs f rmed rein. pist n o erat n in h a d lin r a d a s a 5 in seerat ns the said stcn 4- Tithe c i 2 meriee amain y inderbhe e. hich i 01 t th ri ht s d ig- 1) the eQ and end se e blac 1. is secu ed t the 9: 6. i of sa d 9 ncl r blocs r. e ns'of stu be Th cam s a i m n ed e ta on n a ned olle ea n .9 nd B mean-tee t e ce tra openin -s o the duc rtions and 12 o c inder b ck :6 an ve b oc .7 espe ti el A11 .0 1 se n devic [3: t e inthe ce.ntra p nir. e o reduced se o ea th lef hend en (F 1 thereo and am use a in m mber 5, s a t al U hape in cross-section. having packing material iii-provided. therein, whichirictionally engages the shaft .5. Ete nal-1y threaded ope i s H eprevi in the reduced portion H ,of cylinder block G- to enable attafihmentof the pump I to any suitable supp t n str tur not sh wn fihait 5.1mm e upled t the drive shaft f an electric .motor (not shown) or toany ,ot h er suitable power mechanism. 'ghatt, ;.'.i has formed thereon intermediate itsends an eccentric or cammember 2-0.

Cam member 20, as shown more particularly .in Figs. 1 and 3, is provided with an enlarged. reli y wide cylindri al interme ate po tion 2 nd a a r =Q ;.red ed. re at ve nar ow c lindr calend port on 2.5 21 i ass mb h p riphery-c in e med ate io 3' e a s th inn arcuate surfaces v23 of the slip persz l pivotally attached to theinner ends of the pistons 4.

Th duce portio s 2 ;5. in assembl have se u ed thereto rin 26,16. xEec in 2. ha an nwa s y e ten ng f a ge 2 provid d t ere- 0n,.1 h nn rper phe y o w i h q tm n w th he periph y pf t ed te pqrtion 1 .2 o m ember men-annu a .rece sZB- As sh w-1 .19. 1 .partieulafl in n -l and t e a n l e see .1 re ei e theu e dge .2 pffi'l p e s 2A a dcons mte rcu r snid sp r h il t r- P PE .flenses 2 ..-2,-1.Q. ;r ne$ 2:6. 25 Wis-see eta n t lippe s i p ition onca v e .t i

p Each slipper 24 has formed thereon an elongated rounded retaining member ;3 0 which ;in;as- .semb y ex end into a cqr espend ne y s ap slot-3;!v providedat the lowerend-of anassociated piston. To assemble :the slipper iii-n position .01 he said piston, the rounded memberrin is simply-inserted inslot 3:! and moved-lengthwise thereof until reaching the position shown in Fig. 1. Each piston 4 has provided intermediate the ends thereof a pair of downwardly and outwardly inclining passages 32 and 33 which communicate with a reduced vertical passage 34. Passage 34 terminates in an enlarged upper portion 35 having outlet passages 36 and 3'! extending outwardly from either side thereof, as shown more particularly in Fig. 6.

A seat 38 is formed interiorly of each piston 4 at the upper end of reduced vertical passage 34 for a ball valve 39. The enlarged passage 35 terminates in an annular shoulder 48 forming a seat for a valve stop disc 4|. Disc 4| is circular in construction and has provided centrally thereof a projection 42 which limits the upward movement of ball valve 39. Disc 4| has also provided therein a pair of openings 43 and 44, as shown in Fig. 6, through which fluid may pass as will appear more fully hereinafter. A spring retaining ring 45, which in assembly seats in an annular recess 46 provided near the upper end of piston 4, retains disc 4| in position on shoulder 40.

As shown in Figs. 1 and 2, each cylinder 3 terminates in an enlarged portion 48 and in a still further enlarged internally threaded portion 49. A plug 50 is secured in the enlarged threaded portion 49 of each cylinder 3 and closes the outer end thereof. By this construction machining of the cylinders 3 and assembly of the various elements of the pump generally are facilitated. Communicating with the enlarged portion 48 of each cylinder 3 is a passage 5| which communicates with an enlarged passage 52 terminating in a further enlarged internally threaded passage 53. A plug 54 is secured to the internally threaded passage 53, as shown in Fig. 1, and closes the outer end thereof. The enlarged passage 52 associated with each cylinder 3 communicates with a circular passage 55, which in turn extends around the periphery of the rim portion 56 of casing 2. A seat 51 is provided at the left hand end (Fig. l) of enlarged passage 52 for a ball valve 58. Plug member 54 has secured to the inner end thereof a spring seat 59 for receiving one end of a coil spring 60, the other end of the latter of which engaging ball valve 58 to retain the said valve upon its seat 51. The compression of spring 68 may be varied by adjusting plug 54.

The lower end 6| of easing 2 has provided therein a chamber 63 which is connected-by a relatively short communicating passage 64 to circular passage 55. Circular passage is also connected to a discharge port 65 to which a discharge pipe (not shown) may be attached. A seat 66 is provided between chamber 63 and passage 64 for a ball relief valve 61. A coil spring 68 extends between valve 61 and an adjustable spring seat 69. Spring seat 69 engages the inner end of a plug 19 which closes the left hand end (Fig. 1) of chamber 63. A set screw 1| making threaded engagement with the internally threaded central opening of plug 18 engages the outerside of spring seat 69. Thus to adjust the compression of spring 68 it is only necessary to adjust set screw 1| toward or away from spring seat 69. To prevent accidental movement of adjusting screw H, a cap member 12 is provided thereon, as shown in Fig. 1.

From the foregoing description it is seen that should the pressure in pump I exceed a predetermined value as determined by the pressure of spring 68, valve 61 will move away from its seat 66 and permit the fluid in passage 55 to enter 4 chamber 63, causing an immediate reduction of the pressure in the system.

Fluid enters the pump through the inlet port 16 provided centrally of cover block 7. Port 16 communicates with a passage H provided in shaft 5 near the right hand end thereof. The inner end of passage 11 is curved upwardly, as shown at 1,8, and terminates in a transverse passage 19 provided near the upper end of cam member 28. Thus fluid entering the pump through port 75 flows through passages l1 and 19 and discharges from either end of the latter into a central cham ber 88 of casing 2. The fluid completely fills chamber and then flows into the interior of pistons 4 through passages 32, 33, 34 and 35. This action takes place while the pistons 4 move inwardly toward the axis of shaft 5, at which time valve 39 will have moved away from its seat, permitting the fluid to enter the enlarged passage 35. The fluid flowing into pistons 4 discharges therefrom into the upper enlarged portions 43 of the cylinders 3 through passages 36, 37, 43 and 44. Now as the pistons are moved outwardly by cam 20, valve 39 moves onto its seat, thereby trapping the fluid in the enlarged portion 48. As the pistons 4 move outwardly the fluid in enlarged portions 48 is forced through passages 5|, unseating valves 58 against their springs 68. The fluid then flows into passages 52, and thence into circular passage 55. This pumping action of the pistons 4 takes place successively during a complete rotation of shaft 5, and the fluid so drawn into each chamber 48 discharges therefrom into the associated passages 52, and thence to circular passage 55, as previously described, and then discharges from the pump through port 65. In the event that the pressure of the fluid should exceed a predetermined value as determined by the setting of spring 68, relief valve 61 will move away from its seat to permit the fluid in passage 55 to flow into chamber 63, thereby relieving the pressure in the system.

Fluid is drawn into the pump I through port 16 by the suction action of the pistons 4 as they move toward the center of cam shaft 5. It is also seen that the rotation of cam member 28 of the shaft 5 produces a radial acceleration of the fluid causing it to flow through the transverse passage 19 thereof and into chamber 88 under a positive pressure. During rotation of shaft 5 the fluid in chamber 86 therefore is under a slight pressure which is sufficient to cause it to completely fill the cylinders 3, including the upper enlarged portions 48 thereof during the suction stroke of the pistons 4. The splash action produced by cam member 29 during rotation of shaft 5 also tends to cause the fluid to flow through the passages of pistons 4 and into the cylinders as previously described.

A drain port 8| communicating with chamber 63 is provided at the lower end of casing 2. A plug 82 normally closes opening 8|. Chamber 63 is also connected to central chamber 88 by a communicating passage 84. Thus by removing plug 82 the fluid may be drained from the pump I.

Figs. 9 and 10 illustrate a modified pump construction 90 which consists generally of a casing 9| having formed therein series of radially disposed cylinders 92, pistons 93 operating in the cylinders 92, and a cam shaft 94 for operating the said pistons 93. Casing 9| consists of a main cylinder block 95 and a pair of cover plates 98 and 99, the latter being secured to said cylinder block .by bolts 96 and 91, respectively. Cover plates 98 and 99 are provided with inwardly extending annular flanges Iand IIIIin which-are mounted, respectively, roller bearings. I02" and I03 for the shaft 94.

As shown more particularly in Fig.9, shaft94' is of sectional construction and comprises an axially movable member I04: and a non-axially movable member I05. Member I05 is mounted for rotation in the roller bearing I03 provided in the internal flanged portion IOI andin a second roller bearing I01 provided in the outwardly extending flanged portion I08; of end plate 99. An end retaining plate I09 is secured to the flangedportion I08 in any suitablemanner, such as by cap bolts H0. The member I04 of" shaft 94 is journalled intermediate its ends in' rollerbearing I02, as previously described; and them ner end thereof extendsintothecentral bore I06 of member I05 and is keyed't'o the latterso asto permit relative axial movement of said members. Thus upon rotation of shaft 94; members I04 and I05 thereof will rotatein unison.

A packing gland III secured to-end plate" 98 by bolts H2 is provided to prevent oil leakage past shaft 94.

Member I94 of shaft 94has provided'intermediate the endsthereof anenlargedinclined cylindrical portion H3 which operates in a correspondingly shaped inner bore of an eccentric member He. A cylindrical member H5 is mounted on eccentric member H4, a roller-bearing H5 being provided-therebetween. 'As shown in Fig. 10, the inner ends 93' of pistons-93 are in engagement with the periphery of cylindrical member H5. Thus when shaft member I04 has been adjusted, as will presently appear to move members He and H5 out-ofconcentric position with respect to the axis of shaft 94-, an outward movement will be imparted to pistons93 upon rotation of the said shaft 94.

As shown in Fig. 9, three rows of pistons 93' are provided, there being seven radiallydisposed groups of such pistons as. shown in-Fi'g. 10. It is to be understood, however; that a greater or lesser number of rows ofpistons 93-, aswell'as a greater or-lesser number. of groups'ofsuch pistons, may beprovided without departing from the invention Each group of cylinders 92v terminates at the outer end thereof in-arr enlarged chamber I2I, as shown in Figs. 9 and. 10.

Cylinder block 95 has provided therein near-the opposite sides thereof a circular inletpassage III anda circular outlet passageIIS; A .relatively short transverse communicating passage H9, closed at theouter end thereof by alp'lug I20, connects circular passage. III with each of. the chambers I2I. near the-inner end of passage H9 for. a valve I23. Valve I23. has secured centrally thereofa stem I24 which is guided formovement in: the central bore I25 of plug I20; A coil spri'ngl26 extending between an annular shoulder 12'! provided near the right hand end of passage: H9 and a spring seat I28 secured to' valve stem: I 24 retains valve I23 on its seat I22.

Circular passage H8 is also connected; to each.

chamber I2I by a communicating-passage I30. A seat I3I is provided. near the inn'er end ofreac'h passage I39 for a valve I32. has secured thereto a stem: I33, the outer end of which being guided for movement in the central bore I34 of a plug 135.. Asshown in Fig. 9, theplugs I35 close: the-outer ends .of passages I30. A coil spring I3t-extendsrbetween the inner side: of plug I 35 and valve head I32 and functions.

to retain the said valver-in seatedapositiom.

Avalve seat I22 isprovided,

Each valve; I32

cured to the lower end ofcylinder b1'ock 95 by bolts: I42 retains the pipe I inproper position. Fluid: is: discharged. from pump-90 through a discharge passage' I43 which communicates with circular passage I18. An annular recess- I44: is

provided near'the outer end of'passage I43 for.

receivingtheinner end. I45 oi 'a discharge pipe I43. A pipeclamp I41 secured to the-lower endof'cylinderblock 95 bybolts -I49 secures"thedis charge pipe-m position. y

The cylinder block 95 has provided at thelower end. thereof pedestalsupports: I49 and I50: which may bebolted or otherwisesecured to any sup-- portingstructure.

In operation the pistons 93: are actuated outwardly upon. rotation of shatt' 94;. as previously described; The pressure in chambers I2I operating on vtheouter ends of pistons-93 urges them inwardly. Coil springs I 5i surroundingthe stems I52 providedat the outer. ends'of pistons-93* and extending betweenthe outer walls I53 of chainbers I2I and the outer ends I54 of thesai-dpistons. also operate to urge the latter inwardly.

From the foregoing descripti'cn it isseen that fluid enters thesystem' through pipe I50;- inlet passage I3B. circular passage LIT and communicatingpassages H9. Thepressureof this'fluid' entering the system is sufficient :to overcome the compression of springs I2-6,thereby'opening the associated valves I23 and permitting the fluid to enterchambers I2I. When springs I5I areem-= ployed the pistons are urged inwardly, thereby creating suiiicient suction to open'valves I23i No initial pressure therefore is necessary to unseat the: valves I23. This takes 'place' as the pistons begin. moving inwardly toward the axis of shat-t 94 after a pressure operation. As the shaft continuesits rotation, the pistons 93' are moved outwardly by cam member I I4 and cylindrical memher: I I5, thereby compressing: the fluid in-charnbers" I2I. This pressure-closes valves I23 and opens valves I32, causing the fluid so compressed by'the pistons 93 toenter communicating passages I30 and circular passage I I8, and thence to flow to discharge through outlet passage I43 and discharge pipe I46.

When the parts are in the: position shownin Fig. 9, inclined member IIS iS centrali-Ze'd with respect to eccentric member I I 4' and"the axis of thelatter coincides with that'of shaft 94*.- Consequently no movement will be imparted to pistons93 upon rotationof shaft 394 when the said inclined. member H3 is in this centralized position. However, upon movementof member I34 of shaft .94 to the right or left, as the case may be. a corresponding radial movement will b'e im partedto eccentric member H4, moving the lat-' ter out of concentric position with respect to the axis of shaft 94. Now upon'rot'ation of shaft 96 Y a reciprocatory movement will be impartedto the pistons 93; which function to pump fluid'as previously described. From the'ioregoing de scription it is seen that the greater the axial movement of inclined member I I'3'from its cen'-' tral position, the greater willbe the strokes of l the pistons 93.v

Figs: 11 to 1.7 illustrate a pump I90 of a further modified construction. Pump"- I50 comprises a casing. [5! consistingof a lower-cylinder block portion: I62, having-pedestal supports i=63 -and I64 provided at the lower end thereof and a'cover plate I65. Cover plate I65 is secured to the cylinder block I62 by stud bolts I66. Cylinder block I62 has formed therein at spaced points therealong a series of substantially vertical cylinders I61, in each of which is mounted a piston I68. A cam shaft I69 is provided for operating the pistons I68, and has provided over the length thereof a series of journal portions I16, which, in assembly, are mounted in spaced bearings I1I provided in cylinder block I62 and cover plate I65, as shown more particularly in Figs. 11, 12 and 14. Shaft I69 has formed thereon in spaced relation over the length thereof a series of cam members I12, one for each of the pistons I68. The cam members I12 are so formed on the shaft I89 that the pistons I68 are successively operated during a complete rotation of the cam shaft I69. This. obviously, reduces the effort required to rotate the pump I66.

In the illustrative embodimentthe pistons I68 are of substantially hollow construction and are open at the lower ends thereof, as shown at I13. A coil spring I14 extends between the inner end I 15 of the hollow interior of each piston I68 and the lower reduced end I16 of the associated cylinder I61.

As shown more particularly in Figs. 11 and 12, each piston I68 has provided at theupper end thereof a reduced portion I11, which seats in an aperture I18 provided in a shoe I19. The shoe members I19 are arcuate in construction and are engaged by the cam members I12.

Cylinder block I62 has provided at the opposite sides thereof long inlet and outlet passages I86 and I8I, respectively. These passages extend substantially the entire length of the pump casing I6I and terminate adjacent the cylinder I61 disposed to the left (Fig. 11) of the pump I66. The cylinders I61 extend substantially at right angles to the passages I86 and I 8| and lie substantially midway between said passages, as shown more particularly in Fig. 12. Passages I86 and I 6| are connected by transverse passages I82, which intersect the right hand sides of cylinders I61, as shown more particularly in Fig. 11. Each passage I82 is provided with a reduced inner portion I83 in which is mounted a ball valve I84. Adjacent the reduced portion I83 of passage I82 is a slightly enlarged internally threaded portion I85, which is adapted to receive a correspondingly threaded member I86. Member I86 is provided with a seat I81 at the left hand end thereof for ball valve I84, and is provided with a central opening I88 which establishes communication between reduced portion I83 and a slightly enlarged central portion I89 of passage I82. Adjacent central portion I88 of passage I82 is a slightly enlarged portion I96 in which is mounted a disc member I9I, having a seat I92 at the left hand end (Fig. 14) thereof for a ball valve I93. Member I9I is provided with a central opening I 94, which establishes communication between central chamber I89 and inlet passage I86. A relatively large, internally threaded portion I95 is disposed adjacent portion I96 for receiving a correspondingly threaded plug member I96, which closes the-right hand end (Fig. 14) of passage I62. Plug I96 is provided with an internal bore I91, having openings I98 at spaced points around the inner end thereof to permit the passage of fluid from inlet passage I86 to communicating passage I94. A coil spring I99 extending between the left hand end (Fig. 14) of reduced portion I83 and ball 8 valve I84 retains the latter on its seat I81. Sim ilarly a coil spring 266 extending between the right hand side (Fig. 14) of member I86 and ball valve I98 retains the latter on its seat I92.

It, therefore, is seen that upon movement of pistons I68 toward the axis of shaft I69, suction is created in cylinders I61, causing valves I93 to move away from their respective seats against the action of springs 266, thereby permitting fluid to enter cylinders I61 through communicating passages I93 and central passages I89. The pressure of the fluid entering the system through passage I86 may also be sufficient to unseat valves I93 and thereby permit fluid to enter central portions I89 of passages I82. The fluid entering cylinders I61 in this manner completely fills them and the hollow interiors of pistons I68, as well as the voids in passages I 82. When the pistons I68 are moved downwardly by their cams I12, the pressure created by the compression of the fluid in cylinders I61 closes valves I93 and opens the valves I84 against the compression of springs I99, thereby forcing the fluid from chambers I89 into discharge passage I8I through the passages I88 and I83. This action of the pistons I68 takes place successively and consequently a relatively large quantity of fluid is delivered by the pump I66 at a relatively small operating effort. In the illustrative embodiment five pistons are shown, it being apparent, however, that a greater or lesser number of pistons may be provided, if so desired, without departing from the invention.

In order to prevent excessive pressures in the system a relief valve 265 is provided. As shown in Figs. 11 and 13, a passage 266 connecting inlet and discharge passages I86 and I 8|, respectively, is provided near the right hand end of casing I6I. Passage 266 is provided with a reduced portion 261 near the right hand end (Fig. 13) thereof adjacent discharge passage I 8I. A slightly enlarged, internally threaded portion 268 is disposed between reduced portion 261 and a central portion 269 for receiving a correspondingly threaded member 2I6, having an opening 2II provided centrally thereof which establishes communication between reduced passage 261 and the said central passage 269. Member 2I6 is provided with a seat 2I2 at the left hand end (Fig. 13) thereof for ball valve 265. The central portion 269 of passage 266 communicates with inlet passage I 86. A plug 2 I3 adapted to be held in adjusted position by a set screw 2 I4 is secured to the internally threaded left hand end 2I5 of passage 269. Plug 2I3 has provided centrally thereof a spring seat 2I6 which engages one end of a coil spring 2I1, the other end of which engages the ball valve 265. Accordingly, in the event that the pressure in passage I8I should exceed the desired predetermined value as determined by spring 2I1, valve 265 will move away from its seat and thereby permit fluid from passage I8I to flow into passage I86 through reduced passage 261, opening 2I I and central passage 269. The compression of spring 2I1 may be adjusted by manipulating plug 2I3. After plug 2I3 has been properly adjusted it is held in position by tightening set screw 2I4.

From the foregoing description it is seen that simplified and highly eflicient pumps have been provided. The pumps are constructed of but a few-parts and the elements thereof are so arranged that machining of the cylinders and other parts may be readily performed. It is also seen that assembly of the elements may be expedi tiously efiected, thereby further facilitating the manufacture of the pumps.

It is also apparent that the structures of the pumps are such that pumps of various sizes and capacities may readily be made without undergoing material changes in design.

While the embodiments herein shown and described are adapted to fulfill the objects primarily stated, it is to be understood that it is not intended to limit the invention thereto, since it may be embodied in other forms, all coming within the scope of the claims which follow.

What is claimed is:

1. A pump comprising a fixed casing having one or more cylinders therein, a piston operating in each of said cylinders, a shaft rotatably mounted in said casing, cylindrical cam means carried by said shaft, a slipper pivotally attached to each of said pistons and engaging said cam means, said slipper having freedom for movement with respect to the said piston axially of the said pivot, and means for slidably retaining said slippers in engagement with said cam means, whereby upon operation of the latter by said shaft reciprocatory movements are imparted to said pistons, said retaining means comprising slipper-retaining elements together with means for fixing said elements axially of the shaft with respect both to the cam means and to the slippers so as to immobilize the slippers with respect to the cam means in direction axially of the latter.

2. A pump according to claim 1 including abutment means for preventing movement of the said retaining elements in the casing in the said axial direction.

3. A pump according to claim 2 wherein the slipper-retaining elements consist of a pair of annular members seated in recesses at opposite ends of the cam at opposite sides respectively of the slippers, and having flanges overlapping and closely embracing the edge portions of the latter, said annular members being closely fitted to the cam and to the slippers and having their outer faces in abutment with confronting surfaces of the casing.

4. A pump comprising a casing having a fluid supply chamber and one or more radially disposed cylinders provided therein, a substantially hollow piston operating in each of said cylinders, a shaft mounted for rotation in said casing, cam means mounted on said shaft, said cam having means for operatively connecting said pistons to said cam means whereby upon rotation of the latter alternate suction and pressure movements are imparted to said pistons, means forming inlet passages in said casing, shaft and cam means, said passages communicating with said fluid supply chamber whereby fiuid completely fills the latter, each of said pistons having fluid inlet ports provided therein whereby fluid from said supply chamber enters said cylinders during the suction stroke of said pistons, valve means provided in said pistons for preventing a reverse flow of the fluid entering said cylinders, means forming discharge passages communicating with said cylinders whereby the fluid drawn into said cylinders i discharged therefrom into said discharge passages during the pressure strokes of said pistons, and means for preventing a reverse flow of the fluid in said discharge passages.

5. A cam shaft comprising an elongated body portion, a cam member formed on said body portion, said cam member having a relatively wide portion and a relatively narrow reduced portion at each side of and coaxially with said relatively wide portion, a transverse passage in the relatively wide portion extending to an end of the cam member, and said body portion having a central passage extending inwardly from one end thereof and having an inner radial terminal portion communicating with the transverse passage in said cam member.

ERNST L. MIDGETTE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 603,805 Wood May 10, 1898 948,302 Heard Feb. 1, 1910 1,109,349 Mealey Sept. 1, 1914 1,306,382 Koltz June 10, 1919 1,396,151 Wheeler Nov. 8, 1921 1,910,581 Vickers May 23, 1933 2,164,888 Sassen et al. July 4, 1939 2,243,374 Deschamps May 27, 1941 2,279,645 Sinclair Apr. 14, 1942 2,310,078 Herman Feb, 2, 1943 2,319,718 Brooks May 18, 1943 2,379,156 Johansen June 26, 1945 2,393,128 Temple Jan. 15, 1946 2,404,502 Kenle July 23, 1946 2,404,547 Strid July 23, 1946 2,426,100 Holden Aug. 19, 1947 FOREIGN PATENTS Number Country Date 316,328 Germany 1918 

